1. Field of the Invention
This invention is directed to propagation structures for magnetic bubble domain devices, in general, and to propagation structures which are continuous (i.e. gapless), in particular.
2. Background
Magnetic bubble domain devices are now established as a feasible type of technology for commercial utilization. It is projected that magnetic bubble domain devices may replace many existing devices of known technologies for example, memories. Of course, magnetic bubble domain technology is continuously undergoing evaluation and development to improve the characteristics and the operations thereof. These studies and developments include investigations of various types of propagation structures. Also, investigations have discovered that the effective drive field acting on a bubble is H.sub.eff =.beta.H.sub.xy -.alpha.M.sub.s where .beta. is related to the efficiency of the permalloy pattern to produce local gradients and .alpha. is related to the gradient produced by the magnetostatic interaction between the bubble and the permalloy pattern when no in-plane drive field is applied. In order to maximize the ratio of .beta./.alpha., and in this way reduce the drive field requirements, .alpha. must be reduced. It has been determined that for a disc .alpha. equals zero wherein the .beta./.alpha. ratio approximates infinity.
In view of technological activity directed towards reducing the size of bubbles and, thus, bubble devices, it becomes desirable to reduce the field requirements in driving small bubbles from one element in a propagation structure to the next. As a consequence, investigations are directed toward the possibility of using continuous or gapless propagation structures.
In the past, contiguous (continuous or gapless) structures have been investigated. However, most of the prior art structures have been substantially ineffective or extremely cumbersome to operate. In addition, the continuous structures have frequently exhibited very limited operational characteristics rendering the structures uneconomical or otherwise undesirable for future magnetic bubble domain devices.